Furnace, including ashpit air pressure responsive grate dumping means



Feb. 28, 1950 H. o. BOWSMAN 2,498,787

FURNACE INCLUDING ASHPIT AIR PRESSURE RESPONSIVE GRATE DUMPING MEANS Filed Sept. 12, 1946 3 Sheets-Sheet 1 HARP) 0. BOWJMAN v Filed Sept. 12, 1946 Feb. 28, 1950 H. o. BOWSMAN- 2,498,787

FURNACE INCLUDING ASHPIT AIR PRESSURE RESPONSIVE GRATE DUMPING MEANS 5 Sheets-Sheet 2 /x o I m WWW V AVAVAVAVAWAW I I I I /4/ /4 I M:

ATT'ORNE y Feb. 28, 1950 ows 2,498,787

FURNACE INCLUDING ASHPIT AIR PRESSURE RESPONSIVE GRATE DUMPING MEANS Filed Sept. 12, 1946 3 Sheets-Sheet 3 HARRY 0, BOWSM/IN BY ATTG RNEY Patented Feb. 28, 1950 FURNACE, INCLUDING ASHPIT AIR PRES- SURE RESPONSIVE GRATE DUMPING MEAN S Harry'O. Bowsman, Elgin, 111. Application September 12, 1946, Serial No. 696,454

' 10 Claims. 1

This invention relates to furnaces adapted to burn crushed fuel and particularly fuel crushed to pass through a quarter inch mesh screen.

One object of the invention is to provide a furnace of. the type indicated in which practically complete combustion takes place. Another object of the invention is to provide a furnace in which all parts subject to intense heat consist of refractory material, thus substantially reducing maintenance cost of the furnace and shut-downs for repair. Effectively watercooled material may also be used.

A further object of the invention is to provide a furnace entirely lacking continuously moving parts.

Still another object is to provide a furnace which is simple and sturdy in construction, easy to operate and manipulate, highly emcient, and

in which the relative proportion of fuel and combustion air is readily regulated.

A further object of the invention is to provide a furnace of the type indicated in which the primary air is supplied to the combustion chamber in such a way as to make it rise toward the ignition zone in a broad stream under violent whirling around, thereby avoiding clinker formation that always occurs when the air is introduced in a restricted and concentrated stream.

7 Another object is to provide a furnace in which the dumping of ashes into the ash pit is carried out automatically when a certain amount thereof has accumulated in the combustion chamber.

A further object of the invention is to provide a furnace in which the primary air is effectively and intensely pre-heated before reaching the ignition zone in .the combustion chamber.

Still another object is to provide a furnace in which the fuel is fed to the combustion chamber in such a way as to meet the air stream under the most favorable conditions to secure'a complete, practically explosive combustion in a distinct and restricted ignition zone. 7

Other objects of the invention will be apparent from the following description of a sample embodiment thereof, reference being made to the accompanying drawings in which:

. Fig.- 1 shows a vertical section through the furnace and a boiler in connection therewith,

Fig. 2 shows a vertical section through the lower part of the furnace,

Fig. 3 shows a side view of said lower part of the furnace, r

- Fig. 4- is an exterior elevation showing the operating mechanism for the dump doors, and

Fig. 5 is a 'slde vlew of the same mechanism,

2 with the electrical, circuit shown diagrammatically. Q

It should be clearly understood that the purpose of the drawings and the description thereof is solely to show an example of how the invention may be carried out and that said drawings and description are not intended to limit the inven tion except as indicated by the appended claims.

I The furnace shown in the drawings is largely of a conventional type, the horizontal cross-sec tion being preferably rectangular or square and the walls built up from refractory material in a well known way. 3

In the drawings, the furnace has a front wall I, a rear wall 2, and two end walls, the one in the drawings being indicated by the numeral 3. An interior partition 4 forms the rear wall ofthe combustion chamber 5, and baffles 6, 1, and 8 are arranged between said combustion chamber and a chimney 40, substantially in a known manner and for well known purpose.

The bottom of the combustion chamber has the general shape of an inverted frustum of a pyramid, two of its sides being shown in cross-section at 9 and II] in the drawings. Toward the middle of the combustion chamber, these sloping sides are continued downwards by substantially vertical portions I I, I2, forming an open throat l3.

Below the bottom mouth of 'said throat, two refractory lined. dump doors l4, M, are located in such a way as to provide a continuous slot l5 between the bottom of the throat walls and the top of the dump doors. Saiddump doors l4, M are mounted on parallel shafts l6, I6 and provided with levers l1, l1 at one end outside the furnace, the free ends of said levers l1, l1 being connected by adjustable links l8, l8 to a disc l9 mounted on a shaft 20 and provided, in turn, with'another lever 2|.

The end of the lever 2| is connected, by means of a link 40, to a crank lever 4| on the shaft (not shown) of an electrical motor combined with a speed reducer of any suitable type. The unit comprising the motor and speed reducer is marked 42 and supported on a shelf 43 attached 'tothe wall 3| of an ash pit 30.

An electrical switch 44 is attached to the unit 42 and provided with an actuating arm 45 with a roller 46 which is located in the path of movement of the link 40, as will be explained below.

To the wall 3| of the ash pit 30 another switch 35 is attached, and said switch is of the type that is actuated by-the pressure within the ash pit 30. The switches 35 and 44 are included in separate electrical circuits, as indicated in Fig. 5, the motor in the unit 42 being connected to both circuits, as at 41 and 48.

The throat walls at the bottom of the combustion chamber are surrounded by a channel 25 provided with a slot 26 opening toward the top of the dump doors [4, M, as indicated. A duct 27 connects this channel 25 with the discharge opening of a fan, or blower, 28, located outside the furnace.

A branch pipe 29 leads from the duct 21 to an ejector 50 located at the bottom of the part of the furnace behind the partition 4, and from there the branch pipe continues to the combustion chamber where it penetrates the sloping side 9 some distance above the bottom throat l3.

Beneath the dump doors l4, l4 isv the closed ash pit 30 surrounded by the walls 3 and, as the furnace proper, provided with suitable conventional inspection and operating openings and doors, not particularly shown or indicated.

The, furnace is combined with a, fuel feeder of any suitable conventional type (not shown), the dischar e spout 32 of whi h nters he combustion chamber 5, through its front, wall I. A plurality of. similar spouts, may be provided.

' In operation, the crushed fuel is supplied to the combustion chamber 5 through the spout 3,2,, and, on entering said combustion chamber, is, met by an upwhidly directed stream of air' of a temperature above the ignition point of the fuel. This air s. suppl ed. y the fan 28 t rough he duct 2?. t e channel. 25, slots 26 and I5, and the throat [3. It is preheated by the hot material over which it has to pass. to, the throat l3 and upon entering said throat, by the intensely hot radiation from h m us ion zone prop r in the combustion Chamber.

This excess, of extremely hot air being forced onwards thr u h the combustion chamber 5 creates ideal conditions for complete combustion of the fuel entering through the spout 32. A continuous arcuate surface of ignition is formed across the combustion chamber and from there flames, of combustion gases together with unconsurned coked fuel travelupward into the zone o h ghest heat whe he c mbustion is omple ed:

' Fused ashes. and non-combustible ingredients reduced to, the smallest volume, and greatest density' ride on top of the fountain of flame and drift to the side walls of the combustion chamber where they sink down along the side walls and ontothedllmp doors [4. Here, this material piles up in the middle of the throat, the incoming air from the sides. shaping the pile into a heap narrow ng towards t e p.

When this. pile has attained a certain size it begins to obstruct the admission of air, thus causing an increase of the pressure within the ash pit 3!], This increased pressure actuates the switch 3-5 causing it to, close and thus start the motor. The rotation of the motor causes the crank arm M to move in the direction indicated by the arrow 49; thus swinging the lever 2| towards the left in Fig. 4 through the intermediary of the link 40.

The movement of the lever 24 with the disc t9. pulls the upper ends of the levers IT towards each other, as willreadily be seen from Fig. 4, thus causing the shafts Hi to rotate and to swing the dump doors downwards to open position. The ashes accumulated on the dump doors are thus forced to fall down into the ash pit, thereby relieving the excess pressure Within said ash pit.

- As. soon as the. pressure within the ash pit is thus restored to normal, the switch opens. However, the motor continues its rotation due to the fact that the switch 44 which is normally maintained in open position by the end of the link pressing against the roller 46, is automatically closed as soon as said lever 40 leaves its normal position at the start of the operation, the rotation of the crank arm 4! being in the direction indicated by the. arrow 49.

When the link 40 again approaches its starting position, the dump doors then being restored to closed position by the return movement of the lever 2 it pushes the arm 45 towards the right in Fig. 4, thus causing the switch 44 to open and interrupt the rotation of the motor.

The combustion gases are caused by the baflle 6 to make a sharp turn downwards on their way to the chimney 4! and this causes fuel particles carried with said gases to fall down toward the ejector from where they are carried by the airsstream in the ranch pip .8. bac tothe combustion chamber 5. be ow he. n tion s itiaoe in said chamber. The combustion obtained in a furnace according to. the. invention. is praotically comp ete.

The remarkable improvements. in efficiency by the present. invention over similar furnaces previously known are probably due. mainly to the improved method of supplying the air through a slot around the throat whereby a large. volume of air is continuously subjected to thev intense. heat radiation from the ignition zone above and thus Very efiiciently preeheated.

The improved economy of the, furnace accord ing to the invention also depends upon the fact t at o o ly he. a l o th c mbustion cha ber but also the. dump doors. may be lined with refractory material, thus avoiding the necessity o. subieo ca t iro grate bar and the. ke to. h intense heat. Also, there are no; continuously moving parts such as. moying grates which have hithorto been common in furnaces of this. type. Instead. f he r ra t r li in o he fu nace, awater-w ll d in mayb us d Conventional means. are used for automatic. or nd contro l pr ort on e of theue te d an a r upplrl Almost any grade of crushed coal, can e succe sfully used in this furnace since, whatever heat value theo ai as w l e uti iz d to. the limit and ashes. will be efiectively and automatically dumped as soon as they accumulat on, the dump doors in sufficient. quantities, to obstruct. the flow of i I claim:

n a urnac or burn ng. crush d i c e s fo mi g a combustion ch mbon a s a ash pit. b neath said. combustion c ambon, mea forming a throatatt-he, bottom of aid combustion chamb r nd adapted. o ac umul te ashes... dumb doo beneath h ower ond fsaidi hroat. mean forming a slot between the. lower end, of the hroat. nd. a d dumb doors, or admittan i t he h oat. m ansior sup y n P essure a r o said a h nit. eans f feed n fuel to the mbust n hamben and; m an or,

automatically opening and closing the dump doors, in dependence upon the air pressure in the. ash pit.

2. In a furnace forburning crushed fuel; means. forming a combustion chamber; means forfeeding fuel to said combustion chamber, a sealed ashpit beneath the combustion chamber, means for supplying air under pressure to said ashpit. inwardly sloping wal-lsat the'lower part of said combustion chamber, means forming athroat connecting "said combustion chamber with said ash pit and adapted to accumulate ashes, dump doors spaced apartfrom the bottom end of said throat, means for opening and closing said dump doors, and means controlled by the air pressure in the ash pit for actuating said opening and closing means.

3. In a furnace for burning crushed fuel, means forming a combustion chamber, means for feeding fuel to said combustion chamber, a sealed ash pit beneath the combustion chamber, means for supplying air under pressure to said ash pit, inwardly sloping walls at the lower part of said combustion chamber, means forming a throat connecting said combustion chamber with said ash pit and adapted to accumulate ashes, dump doors spaced apart from the bottom end of said throat so as to form a slot therebetween for admittance of air to the throat, hinges supporting said dump doors so as to permit them to swing downwards and outwards from closed position, means for swinging said dump doors on said hinges to open or to closed position, and means controlled by the air pressure in the ash pit for actuating said swinging means.

4. In a furnace for burning crushed fuel, means forming a combustion chamber, means for feeding fuel to said combustion chamber, a sealed ash pit beneath the combustion chamber, means for supplying air under pressure to said ash pit, inwardly sloping walls at the lower part of said combustion chamber, means forming a throat connecting said combustion chamber with the ash pit and adapted to accumulate ashes, dump doors spaced apart from the bottom end of the throat so as to form a slot therebetween for admittance of air to the throat, a duct surrounding said throat and connected with the pressure air supply source, a slot in said duct facing the top of said dump doors around said throat, means for opening and closing the dump doors, and means controlled by the air pressure in the ash pit for actuating said opening and closing means.

5. In a furnace for burning crushed fuel, means forming a combustion chamber, means for feeding fuel to said combustion chamber, a sealed ash pit beneath the combustion chamber, inwardly sloping walls at the lower part of said combustion chamber, the fuel feeding means opening into the combustion chamber above the level of said sloping walls, means forming a throat connecting said combustion chamber with said ash pit at the lower end of the combustion chamber and adapted to accumulate ashes, dump doors spaced apart from the bottom end of the throat so as to form a slot therebetween, a duct surrounding said throat, another duct connecting said first mentioned duct with the primary air supply source, means forming a slot in said first mentioned duct facing the top of and overlying said dump doors when in closed position, whereby air admitted through said slot is diverted outwards to the ash pit and inwards to the throat, hinges supporting the dump doors so as to permit them to swing downwards and outwards from closed position, means for swinging said dump doors on said hinges to open or to closed position, and means controlled by the air pressure in the ash pit for actuating said swinging means.

6. In a furnace for burning crushed fuel, means forming a combustion chamber, a sealed ash pit underneath said combustion chamber, means for feeding fuel to the combustion chamber, means forming a throat connecting said combustion chamber with said ash pit and adapted to accumulate ashes, refractory lined dump. doors spaced apart from the bottom end of said throat, means surrounding said throat for supplying a stream of primary air toward said refractory material, means for diverting part of said air stream toward the ash pit and another part toward the throat, means for swinging said dump doors to open or to closed position, and means controlled by the air pressure in the ash pit for actuating said swinging means.

7. In a furnace for burning crushed fuel, means forming a combustion chamber of substantially rectangular shape in cross-section and having a bottom part substantially in the shape of an inverted frustum of a pyramid, a sealed ash pit underneath said combustion chamber, a lower prolongation of said pyramid forming a throat connecting the combustion chamber with the ash pit and adapted to accumulate ashes, dump doors spaced apart from the bottom end of said throat, refractory lining material on said dump doors, means for feeding fuel to said combustion chamber, means for supplying air under pressure to the ash pit, means for opening and closing said dump doors, and means controlled by the air pressure in the ash pit for actuating said opening and closing means.

8. In a furnace for burning crushed fuel, means forming a combustion chamber, a sealed ash pit beneath said combustion chamber, means for supplying fuel to the combustion chamber and air under pressure to the ash pit, inwardly sloping walls at the lower part of said combustion chamber, means forming a throat connecting said ash pit with the combustion chamber and adapted to accumulate ashes, dump doors below the bottom end of the throat in closed position, means for diverting primary air into the throat along the bottom edge thereof, hinges for said dump doors, means for swinging the dump doors on said hinges to open or to closed position, and means controlled by the air pressure in the ash pit for actuating said swinging means.

9. In a furnace for burning crushed fuel, means forming a combustion chamber, a sealed ash pit beneath said combustion chamber, means forming a throat at the bottom of said combustion chamber and adapted to accumulate ashes, dump doors beneath the lower end of said throat, means forming a slot between the lower end of the throat and said dump doors, means for feeding fuel to the combustion chamber, means for supplying pressure air to said ash pit and through said slot to the throat and combustion chamber to effect intense pre-heating of said air to the combustion chamber to cause it to ignite the fuel, and means for automatically opening and closing the dum doors in dependence upon the air pressure in the ash pit.

10. In a furnace for burning crushed fuel, means forming a combustion chamber, means for feeding fuel to said combustion chamber, a sealed ash pit beneath the combustion chamber, inwardly sloping walls at the lower part of said combustion chamber, means forming a throat connecting said combustion chamber with said ash pit and adapted to accumulate ashes, means for supplying air under pressure to the combustion chamber through said throat to cause intense pre-heating of said air mainly through radiation from an ignition zone established in the combustion chamber above the throat, dump doors spaced apart from the bottom end of said throat, means for opening and closing said dump doors, and means controlled by the air pressure in the ash pit for actuating said opening and closing means.

HARRY O. BOW SMAN REFERENCES CITED The following references are of record in the file of this patent:

'UNITED STATES PATENTS Number 

